γ-cyclodextrin metal-organic framework-activated gold nanoclusters with water solubility as multi-enzyme mimics for simultaneous detection of pesticide and cholinesterase activity

Cyclodextrin metal-organic framework (CD-MOF) with environmentally friendly components has attracted enormous attention in the past few decades. However, the fragile aqueous stability has limited its application in aqueous catalysis. In this work, we have devised a novel strategy to cope with the problems by introducing the well-defined gold nanoclusters (AuNCs) onto the cyclodextrin ligand through host-guest chemistry. The combination with AuNCs endowed the fragile CD-MOF with excellent multi-enzyme mimicking catalytic abilities, including peroxidase (POD), oxidase (OXD), catalase (CAT) and glucose oxidase (GOx)-mimetic activities. Furthermore, based on its intrinsic POD-like activities, by constructing the typical enzyme cascade reaction, a colorimetric sensor based on Au₃₈/γ-CD-MOF was developed for the rapid and sensitive of carbaryl and butyrylcholinesterase (BChE) activity, respectively. In addition, combined with the smartphone, a portable paper-based sensor was developed, which could realize the on-site and semiquantitative detection of pesticide residues by identifying the RGB value. This low-cost and easy-operation portable assay shows great potential for online detection of pesticides exposure and monitoring other disease biomarkers.